Rankine cycle with multiple configuration of vortex

ABSTRACT

A method and system for improving the efficiency of a Rankine cycle. The system comprises an accumulator that stores a working fluid, a feed pump that pumps the working fluid from the accumulator into a boiler for heating the working fluid to form a dry saturated vapor. The system includes a turbine that expands the dry saturated vapor for generating power and condensing the dry saturated vapor into a volume of wet vapor, at least one vortex tube separating the wet vapor into a higher temperature component (T H ) at hot side and a lower temperature component (T C ) at cold side. The system further includes at least one heat exchanger for exchanging heat from the higher to lower temperature components. The vortex tube is adaptable to function in multiple configurations to increase the change in higher and lower temperature components by reducing the quantitative value of the lower temperature component.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the provisional application No.:61/147,421 filed on Jan. 26, 2009.

FEDERALLY SPONSORED RESEARCH

Not Applicable

SEQUENCE LISTING OR PROGRAM

Not Applicable

STATEMENT REGARDING COPYRIGHTED MATERIAL

Portions of the disclosure of this patent document contain material thatis subject to copyright protection. The copyright owner has no objectionto the facsimile reproduction by anyone of the patent document or thepatent disclosure as it appears in the Patent and Trademark Office fileor records, but otherwise reserves all copyright rights whatsoever.

BACKGROUND

The present invention relates in general to thermodynamic cycles, andmore particularly, to a method and system for improving the efficiencyof the Rankine cycle.

The Rankine cycle, which is a standard thermodynamic cycle, is proposedand developed today for an ever-widening variety of applications,including electric power generation and other refrigerationapplications. In the Rankine cycle, the working fluid is vaporized usingan available heat source and the vapor may expand across the turbine torelease energy to perform work. Thereafter, the vapor is condensed usingan available cooling medium and recirculated in the closed system.

There are a variety of known methods for improving the efficiency of theRankine cycle. A method of intensifying heat in a reversed Rankine cycleand a reversed Rankine cycle apparatus for conducting the heat has beenproposed in U.S. Pat. No. 4,646,524 issued to Kawashima (A reversedRankine cycle system wherein a vortex tube is disposed between thecompressor and the condenser in a reversed Rankine cycle). Thesuperheated vapors of coolant at a high pressure discharged from thecompressor are taken out while separating them by the vortex tube intohigher and lower temperature components through energy separation. Thismethod was to render most of the portion thereof into superheated vaporsof coolant at a higher temperature and the remaining portions intovapors of coolant at a lower temperature, respectively. The superheatedvapors of coolant separated into the higher temperature side areintroduced into the circuit on the higher temperature side of thecondenser and condensated therein, while the vapors of coolant separatedinto the lower temperature side are recycled to the system. Heat may besupplied from atmospheric air, or from the compressor, to vapors ofcoolant from the lower temperature side of the vortex tube;alternatively, in the case where the temperature of the coolant on thelower temperature side is high, excess heat may be recovered therefromby a heat exchanger for heat absorption.

U.S. Pat. No. 4,841,721 issued to Patton, discloses an improved thermalefficiency power plant for converting fuel energy to shaft horsepower.The conventional combustor of a gas turbine power plant is replaced by adirect contact steam boiler, modified to produce a mixture ofsuperheated steam and combustion gases. Combustion takes placepreferably at stoichiometric conditions. The maximum thermal efficiencyof the disclosed plant is achievable at much higher pressures thanconventional gas turbines. Uses of multi-stage compression turbines withintercooling and regeneration is utilized along with a vapor bottomingcycle to achieve a thermal efficiency greater than 60% with a maximumdrive turbine inlet temperature of 160° degrees Fahrenheit.

U.S. Pat. No. 6,230,480, issued to Tagawa, discloses a system and methodfor increasing the specific output of a combined cycle power plant andproviding flexibility in the power plant rating, both without acommensurate increase in the plant heat rate. The present inventiondemonstrates that the process of upgrading thermal efficiencies ofcombined cycles can often be accomplished through the strategic use ofadditional fuel and/or heat input. In particular, gas turbines thatexhaust into HRSGs can be supplementally fired to obtain much highersteam turbine outputs and greater overall plant ratings, but without apenalty on efficiency. This system and method by in large defines a highefficiency combined cycle power plant that is predominantly a Rankine(bottoming) cycle. Exemplary embodiments of the present inventioninclude a load driven by a topping cycle engine (TCE), powered by atopping cycle fluid (TCF) which exhausts into a heat recovery device(HRD). The HRD is fired with a supplementary fuel, or provided anadditional heat source, to produce more energetic and/or larger quantityof the bottoming cycle fluid (BCF) which is used to power a bottomingcycle engine, (BCE) which drives a load (potentially the same load asthe topping cycle engine). Energy contained in either the TCF or BCF isused to power the TCE and BCE respectively, but these fluids, and/ortheir respective engine exhausts, may also be used to support a widevariety of cogeneration applications.

In some methods, reducing the super-heated vapors for the improvement ofthe Rankine process can be done by spraying water. Such type ofarrangement is utilized only in relatively large power plants. A majorproblem within the conventional system and the method for improvement ofRankine cycle is low efficiency. The main reason for low efficiencieswas that heat must be transferred in all four processes through gasfilms on heat transfer surfaces. Since gas films offer relatively highresistance to heat transfer, the mean cycle temperatures was very muchlower than the theoretical temperature. The resulting low thermalefficiency together with high maintenance problems and high engine bulkled to the disuse of these engines.

In some methods, the Rankine cycle is limited by the working fluid usedand small temperature change between the higher and lower temperaturecomponents. Thus, the system has to increase the turbine inlettemperature and dump the excess heat to the environment at 30° C.

It is therefore, an object of the present invention is to provide amethod and a system for improving the efficiency of the Rankine cycleutilizing vortex tubes in multiple configurations. Another object of theinvention is to increase the change in temperature by reducing thequantitative value of the lower temperature components utilizing vortextubes in multiple configurations. Other objects of the present inventionwill become better understood with reference to appended Summary,Description and Claims.

SUMMARY

The present invention is a method and system for improving theefficiency of a Rankine cycle. The system comprises an accumulatordefined to form a reservoir for storing a working fluid, a feed pumpdesigned to pump the working fluid from the accumulator, a boiler forheating the working fluid pumped by the feed pump to form a drysaturated vapor. The system includes a turbine adapted to expand the drysaturated vapor for generating power and condensing the dry saturatedvapor into a volume of wet vapor, at least one vortex tube having a hotside and a cold side for separating a wet vapor into a highertemperature component (T_(H)) and a lower temperature component (T_(C)).The system further includes at least one heat exchanger for exchangingheat from the higher temperature component and the lower temperaturecomponent. A mixer that is adapted to combine the higher temperaturecomponent and the lower temperature component. The vortex tube isadaptable to function in multiple configurations for reducing thequantitative value of the lower temperature component (T_(C)).

The refrigerant liquid or the working fluid is pumped from theaccumulator to the at least one vortex tube. The heat exchanger warmsand the higher temperature component from the hot side of the vortexwill be cooled. Similarly, the mixed gas in the mixer is cooled from thecold side of the vortex tube. The resultant wet vapor flowing into theaccumulator may be below 75° F. at the controlled pressure of 93 psiaand may condense into liquid that is pumped by the feed pump into thehot heat exchanger and into the pump. This configuration is able toconserve much of the heat produced by the boiler and thereby increaseefficiency. Since the feed pump requires energy and there is a system ofheat loss to the environment, expected efficiency is in the 30% range.The system further includes an oil separator arranged proximate theturbine which deposits oil into the feed pump for the regeneration ofthe dry saturated vapor. An improvement to a Rankine cycle, in which avortex tube in multiple configurations is expressed in degrees Kelvin,for example η=1-303.15° K(30° C.)/838.15° K(565° C.)=63.8%.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flow diagram of the basic construction of the presentinvention.

FIG. 2 is a flow chart illustrating an improvement to Rankine cycle.

FIG. 3 is a flow diagram of another embodiment of the present invention,illustrating another configuration of the vortex tube.

FIG. 4 is a flow diagram of yet another embodiment of the presentinvention, illustrating still another configuration of the vortex tube.

FIG. 5 is a graphical representation of the Carnot efficiency as afunction of T_(C)/T_(H) wherein the temperature is constant at 90° C.

REFERENCE NUMERALS

10 . . . Diagrammatic representation of a method according to thepresent invention

12 . . . Accumulator

14 . . . Feed pump

16 . . . Boiler

18 . . . Turbine

20 . . . At least one vortex tube

22 . . . Hot side of the vortex

24 . . . Cold side of the vortex

26 . . . At least one heat exchanger

28 . . . Mixer

30 . . . Oil separator

40 . . . Flow chart illustrating an improvement to Rankine cycle

42 . . . Pumping working fluid from an accumulator

44 . . . Heating working fluid to form a dry saturated vapor

46 . . . Expanding the dry saturated vapor to form wet vapor

48 . . . Introducing wet vapor into at least one vortex tube andseparating of wet vapor

50 . . . Transferring of a higher temperature component

52 . . . Transferring of a lower temperature component

54 . . . Condensing the components into a saturated liquid

56 . . . Repeating the steps in blocks 48, 50 and 52

60 . . . Flow diagram of another embodiment of the present invention

70 . . . Flow diagram of yet another embodiment of the present invention

80 . . . Graphical representation of the Carnot efficiency

DETAILED DESCRIPTION

Referring to the drawings, a preferred embodiment illustrates a methodand a system for improving the efficiency of a Rankine cycle andgenerally indicated in FIGS. 1 through 4. Referring to FIG. 1, the majorcomponents that facilitate the method for improving the efficiency of aRankine cycle are shown in a diagrammatic illustration 10. The systemcomprises an accumulator 12 defined to form a reservoir for storing aworking fluid, a feed pump 14 designed to pump the working fluid fromthe accumulator 12, a boiler 16 for heating the working fluid pumped bythe feed pump to form a dry saturated vapor. The system includes aturbine 18 adapted to expand the dry saturated vapor for generatingpower and condensing the dry saturated vapor into a volume of wet vapor,at least one vortex tube 20 having a hot side 22 and a cold side 24 forseparating a wet vapor into a higher temperature component (T_(H)) and alower temperature component (T_(C)). The system further includes atleast one heat exchanger 26 for exchanging heat from the highertemperature component to the lower temperature component. A mixer 28that is adapted to combine the higher temperature component and thelower temperature component. The vortex tube 20 is adaptable to functionin multiple configurations for reducing the quantitative value of thelower temperature component (T_(C)). The accumulator 12 maintains a highefficient operation of the feed pump 14. The temperature of the systemmay be 90° C. or below.

With reference to FIG. 1, the refrigerant liquid or the working fluid ispumped from the accumulator 12 to the at least one vortex tube 20. Theheat exchanger warms, and the higher temperature component from the hotside of the vortex 22 will be cooled. Similarly, the mixed gas in themixer 28 is cooled from the cold side of the vortex tube 24. Theresultant wet vapor flowing into the accumulator 12 may be below 75° F.at the controlled pressure of 93 psia and may condense into liquid thatis pumped by the feed pump 14 into the hot heat exchanger and into thepump 14. This configuration is able to conserve much of the heatproduced by the boiler 16 and thereby increase efficiency. Since thefeed pump 14 requires energy and there is a system of heat loss to theenvironment, expected efficiency is in the 30% range. The system furtherincludes an oil separator 30 arranged proximate the turbine 18 whichdeposits oil into the feed pump 14 for the regeneration of the drysaturated vapor.

The dry saturated vapor then turns the turbine 18, generating power andresulting in the condensation of the dry saturated vapor into the wetvapor. Due to choked flow, the pressure to the inlet of the vortex tube20 is 233 psia and the temperature due to the reduced pressure is 137°F. The output of the vortex tube 20 is the higher temperature component(hot side) and the lower temperature component (cold side),respectively, depending on the multiple configurations of the vortextubes 20.

FIG. 2 is a flow chart illustrating an improvement to a Rankine cycle40. Initially, an accumulator pumps working fluid through a feed pumpinto a boiler at high pressure as indicated at block 42. The boilerheats the working fluid at a constant pressure to convert the workingfluid into a dry saturated vapor as indicated at block 44. The boiler isheated to a temperature of 180° F. and results in a pressure of 400.28psia. The turbine expands the dry saturated vapor for generating powerand results in the condensation of the dry saturated vapor into wetvapor as indicated at block 46. The wet vapor is introduced into atleast one vortex tube having a hot side and a cold side, then the wetvapor is separated into a higher temperature component at the hot sideand a lower temperature component at the cold side by the vortex tube asindicated at block 48. Then, the higher temperature component isintroduced to a heat exchanger, wherein a specific volume of the highertemperature component is transferred to the boiler and another specificvolume of the higher temperature component in transferred to a mixer asindicated at block 50. The lower temperature component is introduced toanother heat exchanger, wherein a specific volume of the lowertemperature component is transferred to an accumulator and anotherspecific volume of the lower temperature component is transferred to themixer as indicated at block 52. The higher temperature component iscondensed into a saturated liquid and the saturated liquid is collectedin the accumulator 12 as indicated at block 54. The above stepsindicated in the blocks 48, 50, and 52 are repeated for increasing thechange in higher and lower temperature components (T_(H)-T_(C)) byreducing the quantitative value of the lower temperature component(T_(C)). An improvement to a Rankine cycle in which a vortex tube inmultiple configurations is expressed in degrees Kelvin, for exampleη=1-303.15° K(30° C.)/838.15° K(565° C.)=63.8%.

FIG. 3 is a flow diagram of another embodiment of the present invention,illustrating another multiple configuration of the vortex tube asindicated at 60. The accumulator 12 is defined to form a reservoir forstoring a working fluid. The stored working fluid is pumped through thefeed pump 14 into the boiler 16. In the boiler 16, the working fluid isheated to form a dry saturated vapor. The turbine 18 included in thesystem expands the dry saturated vapor for generating power andcondensing the dry saturated vapor into a volume of wet vapor. A vortextube 20 is designed to separate the wet vapor into the highertemperature component and the lower temperature component. Then, a heatexchanger 26 exchanges the heat from the higher temperature to the lowertemperature components. Thereafter, the above steps will continue untilthe change of the higher and lower temperature components is increasedto achieve a reduction of the qualitative value of the lower temperaturecomponent T_(C) that result in higher efficiency of the Rankine cycle.

FIG. 4 is a flow diagram of yet another embodiment of the presentinvention, illustrating another multiple configuration of the vortextube as indicated at 70. Additionally, the system includes a cold heatexchanger 32 with the multiple configuration of the vortex tube 20.

FIG. 5 is a graphical representation of the Carnot efficiency as afunction of T_(C)/T_(H) wherein the temperature is constant at 90° C. asindicated at 80. The improved Rankine cycle for a turbine inlettemperature at 90° C. and a condenser temperature at 30° C. has a Carnotefficiency of 17.3%. If the cold side temperature can be lowered to 0°C., then the Carnot efficiency is raised to 25.5%. The difference isthat the improved Rankine cycle can run off multiple heat sources andcan store heat in a tank of water that allows the cycle to run 24 hoursa day.

All features disclosed in this specification, including any accompanyingclaims, abstract, and drawings, may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

Any element in a claim that does not explicitly state “means for”performing a specified function, or “step for” performing a specificfunction, is not to be interpreted as a “means” or “step” clause asspecified in 35 U.S.C. §112, paragraph 6. In particular, the use of“step of” in the claims herein is not intended to invoke the provisionsof 35 U.S.C. §112, paragraph 6.

Although preferred embodiments of the present invention have been shownand described, various modifications and substitutions may be madethereto without departing from the spirit and scope of the invention.Accordingly, it is to be understood that the present invention has beendescribed by way of illustration and not limitation.

1. A method for improving the efficiency of a Rankine cycle, the methodcomprising the steps of: (a) pumping a working fluid from an accumulatorthrough a feed pump into a boiler at high pressure; (b) heating theworking fluid in the boiler at a constant pressure to convert theworking fluid into a dry saturated vapor; (c) expanding the drysaturated vapor in a turbine for generating power and condensing the drysaturated vapor into a volume of wet vapor; (d) introducing the wetvapor into at least one vortex tube having a hot side and a cold sidefor separating the wet vapor into a higher temperature component (T_(H))and a lower temperature component (T_(C)); (e) introducing the highertemperature component through the hot side to a heat exchanger, whereina specific volume of the higher temperature component is transferred tothe boiler and another specific volume of the higher temperaturecomponent is transferred to a mixer; and introducing the lowertemperature component through the cold side to another heat exchanger,wherein a specific volume of the lower temperature component istransferred to an accumulator and another specific volume of the lowertemperature component is transferred to the mixer; (f) condensing thehigher temperature component into a saturated liquid and collecting thesaturated liquid in the accumulator; and (g) repeating steps (d) through(f) for increasing the change in higher and lower temperature components(T_(H)-T_(C)) by reducing the quantitative value of the lowertemperature component (T_(C)).
 2. The method of claim 1, wherein theworking fluid is a liquid refrigerant.
 3. The method of claim 1, whereinthe boiler is heated to a temperature of 180° F. and in a pressure of400.28 psia.
 4. A system for improving the efficiency of a Rankine cycleutilizing at least one vortex tube in multiple configurations, thesystem comprising: an accumulator defined to form a reservoir forstoring a working fluid; a feed pump designed to pump the working fluidfrom the accumulator; a boiler for heating the working fluid pumped bythe feed pump to form a dry saturated vapor; a turbine adapted to expandthe dry saturated vapor for generating power and condensing the drysaturated vapor into a volume of wet vapor; at least one vortex tubehaving a hot side and a cold side for separating the wet vapor into ahigher temperature component (T_(H)) and a lower temperature component(T_(C)); at least one heat exchanger for exchanging heat from the highertemperature component to the lower temperature component; and a mixeradapted to combine the higher temperature component and the lowertemperature component; whereby the vortex tube is adaptable to functionin multiple configurations for reducing the quantitative value of thelower temperature component (T_(C)).
 5. The system of claim 4, whereinthe working fluid is a liquid refrigerant.
 6. The system of claim 4,wherein the boiler is heated to a temperature of 180° F. and in apressure of 400.28 psia.
 7. The system of claim 4, wherein the systemfurther includes an oil separator arranged proximate the turbine whichdeposits oil into the feed pump for the regeneration of the drysaturated vapor.